Physiological reactions of a passenger to transportation conditions

The effect of transportation conditions on the performance capacity of a passenger were studied, in order to establish the time for his most rapid inclusion in production activity after the trip. It was concluded that the transportation conditions impair the functional condition of the passenger's organism. The restoration of the functional state to the initial level occurs mainly in the space of one day. It is shown that it is necessary to take into consideration the adaptation of the organism during transfer to another climate zone

Electronic correlations and crystal structure distortions in BaBiO3

BaBiO3 is a material where formally Bi4+ ions with the half-filled 6s-states form the alternating set of Bi3+ and Bi5+ ions resulting in a charge ordered insulator. The charge ordering is accompanied by the breathing distortion of the BiO6 octahedra (extension and contraction of the Bi-O bond lengths). Standard Density Functional Theory (DFT) calculations fail to obtain the crystal structure instability caused by the pure breathing distortions. Combining effects of the breathing distortions and tilting of the BiO6 octahedra allows DFT to reproduce qualitatively experimentally observed insulator with monoclinic crystal structure but gives strongly underestimate breathing distortion parameter and energy gap values. In the present work we reexamine the BaBiO3 problem within the GGA+U method using a Wannier functions basis set for the Bi 6s-band. Due to high oxidation state of bismuth in this material the Bi 6s-symmetry Wannier function is predominantly extended spatially on surrounding oxygen ions and hence differs strongly from a pure atomic 6s-orbital. That is in sharp contrast to transition metal oxides (with exclusion of high oxidation state compounds) where the major part a of d-band Wannier function is concentrated on metal ion and a pure atomic d-orbital can serve as a good approximation. The GGA+U calculation results agree well with experimental data, in particular with experimental crystal structure parameters and energy gap values. Moreover, the GGA+U method allows one to reproduce the crystal structure instability due to the pure breathing distortions without octahedra tilting

Electric Field Effect in Atomically Thin Carbon Films

We report a naturally-occurring two-dimensional material (graphene that can be viewed as a gigantic flat fullerene molecule, describe its electronic properties and demonstrate all-metallic field-effect transistor, which uniquely exhibits ballistic transport at submicron distances even at room temperature

Stacking boundaries and transport in bilayer graphene

Pristine bilayer graphene behaves in some instances as an insulator with a transport gap of a few meV. This behaviour has been interpreted as the result of an intrinsic electronic instability induced by many-body correlations. Intriguingly, however, some samples of similar mobility exhibit good metallic properties, with a minimal conductivity of the order of $2e^2/h$. Here we propose an explanation for this dichotomy, which is unrelated to electron interactions and based instead on the reversible formation of boundaries between stacking domains (`solitons'). We argue, using a numerical analysis, that the hallmark features of the previously inferred many-body insulating state can be explained by scattering on boundaries between domains with different stacking order (AB and BA). We furthermore present experimental evidence, reinforcing our interpretation, of reversible switching between a metallic and an insulating regime in suspended bilayers when subjected to thermal cycling or high current annealing.Comment: 13 pages, 15 figures. Published version (Nano Letters

Tetraquarks composed of 4 heavy quarks

In the current work spectroscopy and possibility of observation at the LHC of tetraquarks composed of 4 heavy quarks is discussed. Tetraquarks concerned are T_{4c}=[cc][cc]$, T_{4b}=[bb][bb] and T_{2[bc]}=[bc][bc]. By solving nonrelativistic Schroedinger equation masses of these states are found with the hyperfine splitting accounted for. It is shown that masses of tensor tetraquarks T_{4c}(2++) and T_{2[bc]}(2++) are high enough to observe these states as peaks in the invariant mass distributions of heavy quarkonia pairs in pp -> T_{4c}+X -> 2J/\psi+X, pp -> T_{2[bc]}+X -> 2B_{c}+X and pp -> T_{2[bc]}+X -> J/\psi\Upsilon(1S)+X channels while T_{4b} is under the threshold of decay into a vector bottomonia pair.Comment: 8 pages, 3 figures, in the revised version several refences were adde

Unconventional quantum Hall effect and Berry’s phase 2pi in bilayer graphene.

There are known two distinct types of the integer quantum Hall effect. One is the conventional quantum Hall effect, characteristic of two-dimensional semiconductor systems, and the other is its relativistic counterpart recently observed in graphene, where charge carriers mimic Dirac fermions characterized by Berry’s phase pi, which results in a shifted positions of Hall plateaus. Here we report a third type of the integer quantum Hall effect. Charge carriers in bilayer graphene have a parabolic energy spectrum but are chiral and exhibit Berry’s phase 2pi affecting their quantum dynamics. The Landau quantization of these fermions results in plateaus in Hall conductivity at standard integer positions but the last (zero-level) plateau is missing. The zero-level anomaly is accompanied by metallic conductivity in the limit of low concentrations and high magnetic fields, in stark contrast to the conventional, insulating behavior in this regime. The revealed chiral fermions have no known analogues and present an intriguing case for quantum-mechanical studies